Recovery of sulphur



July 11, 1933 R. F. BACON Ely-.AL 1,917,226

v RECOVERY oF sULPHUn FiledFeb. 2e 1.930

ATTORNEYS Patented `luly 11, 1933 UNITED STATES PATENT OFFICE RAYMOND F. BACON, OF BRONXVILLE, .AND ISAAC BENCOWITZ, OF NEW YORK, N. Y.; SAID BENCOWITZ ASSIGNOR TO SAID BACON' RECOVERY 0F SULPHUR Application iled February 26, 1930. Serial No. 431,459.

This invention relates to the recoveryof sulphur and has for an object the provision of an improved process for recovering sulphur from heavy metal sulphide ores. More particularly, the invention contemplates the provision of an improvedlprocess for recovering sulphur from materials containing one or more sulphides of iron. The invention further contemplates the provision of an improved process for treat-ing heavy metal. sulphide ores such, for example, as ore containing sulphides of iron, copper and nickel.

rlhe process of the present invention involves the treatment of ore or other metal iurgical raiv materials or products containing pyrit-es or other sulphides of' iron, alone or in combination With sulphides of other heavy metals such, for example, as copper and nickel With chlorine for the purpose of obtaining free sulphur and/or separating iron from the mass of material undergoing treatment.

In carrying` out a process in accordance With the present invention, a quantity of ore or other material to be treated is subjected to the action of chlorine und-er such conditions that ferrous chloride and free sulphur are produced. The operation is so conducted that the sulphur produced is vaporized, leaving a residue containing the ferrous chloride together With chlorides of other heavy metals, such as copper and nickel, when the. sulphides of such metals are present in the material undergoing treat-ment. The sulphur produced is condensed and collected as free sulphur. The residue containing ferrous chloride is subjected to the action of chlorine gas to form and vaporize ferrie chloride. The ferrie chloride produced is subjected to the-action of superheated steam to produce hydrogen chloride Which is subjected tothe action of oxygen to produce free chlorine. The chlorine thus produced is returned to the process. n

The invention Will be better understood from a consideration of the accompanying lromvsheet and the following description of the application of the invention to the 'treatment of ore containing sulphides of iron, copper and nickel.

The ore to be treated is subjected to the action of chlorine under such conditions that ferrous chloride and free sulphur are produced. The operation is so conducted that the sulphur produced is vaporized, leaving a residue containing the ferrous chloride together with the chlorides of copper and nickel. The sulphur may be vaporized by means of inert gases introduced With the chlorine or a temperature suiciently high to vaporize the sulphur may be maintained and substantially pure chlorine gas may be employed. The invention contemplates the recovery of chlorine during the course of the process. The chlorine When first recovered may be mixed with inert gases, and the mixture of gases may be introduced into the chlorinating chamber. When the mixture is used, the reaction chamber may be maintained at a temperature above or below the boiling point of sulphur. At either or both temperatures, the reaction may be so controlled that the inert gases aid in sweeping the sulphur from the reaction chamber. A temperature of about 300O C. to 350 may be maintained throughout the entire reaction chamber.

The ore is preferably introduced in a dry, finely divided condition into the interior of a rotary reaction chamber having ore charg ing means at one end and discharging means at the other end, and Which is so constructed and operated that the ore is gradually moved from the charging end toward the discharge end. Chlorine gas alone or mixed With other gases is introduced into the reaction chamber at the end opposite to that at Which the ore is introduced and the ore and sulphur chloride pass through the reaction chamber in counter-current relationship. The ore is preferably ground to provide particles sufliciently small to pass a lOO-mesh screen in order that intimate contact of the sulphur chloride With the sulphide particles may be obtained.

The process is preferably so controlled that a temperature of yabout 450 C. is maintained near the ore charging end of the reaction chambenand a temperature of about 300o C. to 850o C. is maintained near the discharge end of the reaction chamber. The chlorine in any desired concentration and at any desired temperature is introduced into a portion of the reaction chamber which is maintained at a temperature of about 300 C. to 350 C. The chlorine and the metal sulphides react to produce elemental sulphur, ferrous chloride and the chlorides of copper and nickel. The admission of ore and chlorine is preferably so regulated that all of the sulphur liberated is vaporized as elemental sulphur, all of the chlorine admitted is consumed, and substantially all of the iron sulphide is converted to ferrous chloride.

Any ferrie chloride which is produced in the reaction chamber will be vaporized and swept along with the incoming chlorine to meet the entering iron sulphide-bearing material. The ferrie chloride will react with 'the sulphides to form ferrous chloride and sulphur chloride. Sulphur chloride which is formed will also react with the heavy metal sulphides. rlhe reaction between the sulphides and the chlorine is eXothermic and the desired temperatures may be maintained by the heat developed.

The sulphur produced is vaporized and separated from the heavy metal chlorides in the hottest portion of the reaction chamber, and the residue containing the heavy metal chlorides is discharged from the reaction chamber at a temperature of about 300 C. to 350 C. The vaporized sulphur is collected and condensed.

The hot residue containing ferrous chloride is subjected to the action of chlorine gas to produce and vaporize ferrie chloride. rlhe treatment of the ferrous chloride-bearing material is preferably conducted in a rotary reaction chamber which is so constructed and arranged that ferrous chloride-bearing material charged into one end portion will move progressively toward the other end portion during its rotation. The ferrous-chloride bearing material and the chlorine gas are preferably introduced into opposite ends of the reaction chamber and pass through the reaction chamber in counter-current relationship. The ferrous chloride-bearing material 'thus passes gradually into regions of increasing chlorine concentrations and a substantially complete removal of iron from the mass is assured.

The hot residue contains nickel chloride and copper chloride in addition to ferrous chloride and gangue, and it enters the reaction chamber at a temperature of about 300 C. The chlorine employed for treating the ferrous chloride-bearing material comprises, in part at least, chlorine whichis recovered in a subsequent stepof the process from ferric chloride produced during the course of the treatment, and it is contaminated with inert gases which are introduced into the system. The inert gases may be utilized for 2FeCl2 -l- C12: QFeCl3 The chlorides of nickel and copper remain unchanged and do not vaporize to any substantial extent when a temperature between about 300 C. and 350 C. is maintained.

A residue containing the chlorides of copper and nickel and gangue contained in the original ore is discharged from the reaction chamber and it may be treated in any desired manner to separate and recover the valuable components.

rllhe vaporized ferrie chloride is collected and comdensed to eliminate inert gases.

rlhe condensed ferrie chloride is vaporized and subjected to the action of water vapor at an elevated tei'nperature in a suitable reaction chamber. The ferrie chloride is hydrolyzed and ferrie oxide and hydrogen chloride are formed, the reaction proceeding accordl ing to the following equation:

QFQOL; l F9203 i In carrying out the hydrolysis of ferrie chloride, ferrie chloride vapor and super-- heated steam are introduced together into the reaction chamber in such a manner that intimate mixing will result. The vreaction may be conducted conveniently at a temperature of about 300 C. to 400 C. Good results may be obtained if the reaction chamber is maintained at a temperature of about 350 C.

The ferrie oxide will be produced in the form of a fine powder which may be permitted to settle outin the reaction chamber. The gases issuing from the chamber contain hydrogen chloride and water vapor and they are passed through a suitable drying apparatus such, for example, as a packed tower having sulphuric acid trickling therethrough to separate the water vapor and produce dry hydrogen chloride.

The dry hydrogen chloride isA introduced into a catalytic reaction chamber with one to seven times its volume of air, depending on the concentration of the hydrogen chloride available. The air is preheated to a temperature above l20 C. and preferably to a temperature between 520 C. and 530 C.

lf desired, the hydrogen chloride may also be preheated.

The catalytic reaction chamber preferably consists of a tower, or a series of communicating towers packed with porous material having a very large surface per unit of volume such, for example, as pumice, brick, cinders and the like. The packing material should be of such a nature that it will be inert to the reagents and the products of the reaction. The' packing material is covered or impregnated with the catalyst which promotes a reaction between hydrogen chloride vand oxygen, and which may consist of one or more chlorides or sulphates of metals such, for example, as copper and nickel. The salts may be applied as such directly to the packing material or they may be formed in place as, for example, by the action of hydogen -chleride on copper oxide which is distributed throughout the mass. Afor renewing the catalytic mass as its elii ciency becomes reduced. For this purpose two towers, or two series of communicating towers, which may be used alternately are preferably provided.

The apparatus is so constructed that the mass of catalyst bearing material may be maintained at a temperature of from 370 to 400 C. The reaction between the hydrogen chloride and the oxygen of the air is exothermic and it may be so controlled as to permit the proper temperature to be maintained. The reaction will proceed at a temperature as low as 205 C., and a temperature as high as L70" C. may be used advantageously. The temperature at which the reaction is conducted will be governed largely by the nature of the catalyst. The temperature employed should be sufficiently low that excessive volatilization of the catalyst is avoided. The reaction involved in this operation does not proceed to completion. The gases issuing from the reaction chamber will consist of a mixture of hydrogen chloride, water vapor and chlorine.

n view of the fact that the reaction does not readily proceed to completion, it may be desirable to retreat the issuing gases by subjecting them to a drying operation to remove the water vapor and subsequently passing them through a second reaction chamber. This procedure may be repeated two or three or more times if desired. In carrying out the reaction between hydrogen chloride and the oxygen of air it is advisable to carefully control the proportions of air and hydrogen chloride utilized in order to avoid excessive dilution of the resulting chlorine gas and in order to avoid the incorporation of excessive amounts of free oxygen in the resulting chlorine gas.

The gases are washed with water to separate the chlorine and hydrogen chloride. The separated chlorin-e is dried Withsulphuric Means are provided acid, and a portion of the dried gas is utilized for treating the residue containing ferrous chloride. The remainder of the chlorine is utilized for treating additional quantities of the iron sulphide-bearing material.

The sulphuric acid used for drying the hydrogen chloride and chlorine is combined with the water use-d for separating the hydrogen chloride and chlorine and the resulting liquid is heated to recover hydrogen chloride which is returned to the process. The sulphuric acid which has been freed from hydrogen chloride is concentrated and again used for drying purposes. A portion of the steam produced ink concentrating the sulphuric acid is utilized for treating. the ferric chloride. The first fractions obtained -during the concentration ofv the sulphuric acid will contain hydrogen chloride and the use of these fractions in providing superheated steam for treating the ferrie chloride will permit an added recovery of chlorine.

As a result of the treatment of the hydrogen chloride with air, considerable quantities of inert gases, such as nitrogen, are introduced into the system and must be eliminated to avoid excessive dilution. The inert gases will be mixed with the chlorine gas which is recovered, and consequently, they will be returned to the system during the treatment of original ore and during the treatment of the ferrous chloride-bearing residue. Elimination of these gases is effected by condensing the ferric chloride and by condensing the vaporized sulphur.

The process may be conducted continuously. A source of fresh chlorine is provided to compensate for chlorine losses due to leakage and the production of nickel and copper chlorides. The fresh chlorine may be supplied as chlorine gas or hydrogen chloride and the choice will be determined by the relative costs.

The principal reactions involved in the A- process are exothermic and enough heat is provided that no heat need be supplied from outside sources. .Heat generated during the course of the process may be utilized for carrying out the concentration of the sulphuric acid, vaporization of f-erric chloride and other operations in which temperatures must be increased.

Ve claim:

l. The method of treating material containing iron sulphide which comprises sub- ]ecting the material to the action of chlorine under such conditions that ferrous chloride and elemental sulphur are produced and the sulphur is vaporized, subjecting the ferrous chloride to the action of chlorine to form ferrie chloride, subjecting the ferric chloride to the action ofwater vapor to produce hydrogen chloride, treating the hydrogen chloride to recover chlorine and returnffl ing the chlorine thus recovered to the process.

2. The method of treating material containing iron sulphide Which comprises subjecting the material to the action of chlorine yunder such conditions that ferrous chloride and elemental sulphur are produc-ed and the sulphur is vaporized, subjecting th-e ferrous chlori-de to the action of chlorine to form ferric chloride, subjecting the ferric chloride to th-e action of vvater vapor to produce hydrogen chloride, subjecting the hydrogen chloride to the action of air in the presence of a catalyst to recover chlorine, and returning the chlorine thus recovered to the process. i

3. rlhe method of treating material containing iron sulphide which comprises subjecting the material to the action of chlorine under such conditions that ferrous chloride and elemental sulphur are produced and the sulphur is vaporized, subjecting the ferrous chloride to the action of chlorine to form ferric chloride, subjecting the ferric chloride .f to the action of Water vapor to produce hydrogen chloride, treating the hydrogen chloride to recover chlorine, utilizing a portion of the chlorine thus recovered to treat the ferrous chloride, and utilizing the remainder of the recovered chlorine to treat additional iron sulphide-bearing material.

4. rlhe method of treating material containing iron sulphide Which comprises subjecting the material to the action of chlorine under such conditions that ferrous chloride and elemental sulphur are produced and the sulphur is vaporizcd, subjecting the ferrous chloride to the action of chlorine to form ferric chloride, subjecting the ferric chloride l to the action of Water vapor to produce hydrogen chloride, subjecting the hydrogen chloride to the action of air in the presence of a catalyst to recover chlorine, utilizing a portion of the chlorine thus recovered to treat the ferrous chloride, and utilizing the remainder of the recovered chlorine to treat additional iron sulphide-bearing material.

5. In a process for recovering sulphur from iron sulphide-bearing material involving the production of iron chloride and hydrolysis of the iron chloride to produce gases containing hydrogen chloride, the improvement which comprises drying the gases containing hydrogen chloride With sulphuric acid,

heating the sulphuric acid to effect its concentration and produce steam, and utilizing thel steam thus produced in the hydrolysis of the iron chloride.

6. na process for recovering sulphur involving the chlorination of iron sulphide to produce iron chloride, and treatment of the iron chloride to produce hydrogen chloride, the improvement .which comprises treating the hydrogen chloride to produce a mixture of gases containing chlorine and hydrogen chloride, Washing the mixture of gases to separate the hydrogen chloride and chlorine and thereby obtaining a solution of hydrogen chloride, and heating the hydrogen chloride solution with sulphuric acidto recover the hydrogen chloride.

7. The method of treating material containing iron sulphide which comprises subjecting the material to the action of chlorine under such conditions that ferrous chloride and elemental sulphur are produced and the sulphur is vaporized, subjecting the ferrous chloride to the action of chlorine to form and vaporize ferric chloride, condensing the ferric chloride to separate inert gases, subjecting the ferric chloride to the action of Water vapor to produce hydrogen chloride, treating the hydrogen chloride to recover chlorine, utilizing a portion of the chlorine thus recovered to treat the ferrous chloride, and utilizing the remainder of the recovered chlorine to treat additional iron sulphide-bearing material. i

8,. The method of treating material containing iron sulphide which comprises subjecting the material to the action of chlorine under such conditions that ferrous chloride and elemental sulphur are produced and the sulphur' is vaporized, subjecting the ferrous chloride to the action of chlorine to form and vaporize ferric chloride, condensing the ferric chloride to separate inert gases, subjecting the ferric chloride to the action of Water vapor to produce hydrogen chloride, subjecting the hydrogen chloride to the action of air in the presence of a catalyst to recover chlorine, utilizing a portion of the chlorine thus recovered to treat the ferrous chloride, and utilizing the remainder of the recovered chlorine to treat additional iron sulphide-bearing material.

9. The method of treating material containing iron sulphide which comprises subjecting the material to the action of chlorine under such conditions that ferrous chloride and elemental sulphur are produced and the sulphur is vaporized, subjecting the ferrous chloride to the action of chlorine to form and vaporize ferric chloride, condensing the ferric chloride to separate inert gases, vaporizing the condensed ferric chloride, subjecting the vaporized ferric chloride to the action of superheated steam tov produce hydrogen chloride, treating the hydrogen chloride to recover chlorine, utilizing a portion of the chlorine thus recovered to treat the ferrous chloride, and utilizing the remainder of the recovered chlorine to treat additional iron sulphide-b-earing material.

10. The method of treating material containing iron sulphide Which comprises subjecting the material to the action of chlorine under such conditions that ferrous chloride and elemental sulphur are produced and the sulphur is Vaporized, subjecting the ferrous of the chlorine thus recovered to treat the ferrous chloride, and utilizing the remainder of the recovered chlorine to treat additional iron sulphide-bearing material.

In testimony whereof We aliX our signatures.

RAYMOND F. BACON. ISAAC BENCOWITZ. 

